CVE-2025-50646: Dlink Di-8003 Buffer Overflow Vulnerability

CVE-2025-50646 Overview

CVE-2025-50646 is a buffer overflow vulnerability in the D-Link DI-8003 router running firmware version 16.07.26A1. The flaw resides in the /qos_type_asp.asp endpoint, where the web management interface fails to validate the length of the name parameter before copying it into a fixed-size buffer. Remote attackers can send a crafted HTTP request to trigger memory corruption and crash the device, resulting in a denial-of-service condition. The vulnerability is classified under CWE-120: Buffer Copy without Checking Size of Input.

Critical Impact

Unauthenticated network attackers can trigger a denial-of-service condition on affected D-Link DI-8003 devices by sending a single malformed HTTP request.

Affected Products

• D-Link DI-8003 router (hardware)
• D-Link DI-8003 firmware version 16.07.26A1
• Deployments exposing the web administration interface to untrusted networks

Discovery Timeline

• 2026-04-08 - CVE-2025-50646 published to the National Vulnerability Database
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2025-50646

Vulnerability Analysis

The vulnerability exists in the QoS configuration handler exposed at /qos_type_asp.asp on the device's embedded web server. The handler reads the name parameter from the incoming HTTP request and copies it into a stack-allocated buffer without enforcing a length check. When the supplied value exceeds the expected buffer size, adjacent memory on the stack is overwritten, corrupting saved registers and control data used by the request handler.

Because the affected service is the management daemon running on the router itself, a successful overflow halts the device's HTTP service and, in observed conditions, causes the firmware to reset or hang. The CVSS vector indicates impact limited to availability, consistent with a crash-style overflow rather than confirmed code execution. Network reachability to the web interface is the only prerequisite for triggering the bug.

Root Cause

The root cause is missing bounds validation on user-controlled input. The name parameter is copied into a fixed-size buffer without using length-limited string operations such as strncpy or explicit size checks. This pattern is common in SOHO router firmware where CGI handlers parse query parameters using unsafe C string functions.

Attack Vector

Exploitation requires network access to the router's web management interface and no authentication or user interaction. An attacker crafts an HTTP request targeting /qos_type_asp.asp with an oversized name parameter value. Devices exposing the management interface to the internet or to untrusted segments are directly reachable; in segmented environments, an attacker who has already gained a foothold on the local network can pivot to the router. No public proof-of-concept code has been published at the time of writing.

For additional technical context, see the D-Link Security Advisory SAP10505 and the GitHub IoT Vulnerability Collection.

Detection Methods for CVE-2025-50646

Indicators of Compromise

• Unexpected reboots, watchdog resets, or HTTP service unavailability on D-Link DI-8003 devices running firmware 16.07.26A1.
• HTTP POST or GET requests to /qos_type_asp.asp containing an unusually long name parameter.
• Loss of management plane responsiveness coinciding with inbound traffic from untrusted sources.

Detection Strategies

• Inspect web server and reverse proxy logs for requests targeting /qos_type_asp.asp with parameter values exceeding several hundred bytes.
• Deploy network intrusion detection signatures that flag oversized query string or body parameters destined for the router's management interface.
• Correlate router availability alerts with inbound HTTP traffic patterns to identify probing attempts.

Monitoring Recommendations

• Forward syslog and SNMP availability data from the DI-8003 to a centralized log platform for trend analysis.
• Alert on repeated HTTP 5xx responses or connection resets originating from the router's management port.
• Track exposure of the management interface using external attack surface scans to confirm it is not reachable from the internet.

How to Mitigate CVE-2025-50646

Immediate Actions Required

• Restrict access to the DI-8003 web management interface to trusted administrative networks using ACLs or firewall rules.
• Disable remote management over the WAN interface until a vendor patch is applied.
• Inventory affected devices running firmware 16.07.26A1 and prioritize remediation for internet-facing units.

Patch Information

At the time of publication, consult the D-Link Security Bulletin and advisory SAP10505 for the latest firmware availability and remediation guidance. Apply vendor-provided firmware updates as soon as they are released for the DI-8003 platform.

Workarounds

• Place the router's management interface behind a VPN and block direct HTTP access from untrusted networks.
• Enforce source IP allow-lists on the administrative port using upstream firewalls.
• Where business requirements permit, replace the DI-8003 with a supported model that receives current security updates.

# Example: restrict management interface access using an upstream firewall (iptables)
# Allow only the administrative subnet to reach the router's web UI
iptables -A FORWARD -s 10.0.0.0/24 -d <router_ip> -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <router_ip> -p tcp --dport 443 -j DROP